Vivo the parts bin specialist making sure they have too many models to support sufficiently after few months of release. Chinese manufacturers should copy Apple also in longetivity of devices not only looks. Xiaomi and Oneplus do pretty good work in bringing the older models up to date but the same can not be said about others.
Why would they offer 4gb/128gb vs 6gb/64gb???
One number good up and one goes down. My guess is that the facts were not checked.